THE LYMPHATIC NODES 149 



Each lymphatic node consists of a mass of follicular lymphoid 

 tissue inclosed within a fibro-elastic connective tissue capsule. 

 The capsule also contains a little smooth muscle tissue, but this 

 is never so abundant as to form any considerable portion of the 

 fibrous membrane ; in fact, as compared with the somewhat similar 

 capsule of the spleen, that of the lymphatic node is notably defi- 

 cient in smooth muscle. 



An afferent lymphatic vessel, pursuing its course within the 

 capsule, enters the lymphatic node by a number of subdivisions 

 which penetrate the deeper layers of the capsule and open into a 



FIG. 147. TRANSECTION or A CERVICAL LYMPHATIC NODE OF A DOG. 



The denser portions of lymphoid tissue are light in the figure, a, medullary cord of 

 dense lymphoid tissue ; 6, looser lymphoid tissue of the cavernous medulla ; c, capsule ; 

 F, dense lymphoid follicle of the cortex ; HF, fibrous tissue containing the large vr--t -Is 

 of the hilum ; s, peripheral lymphatic sinus ; V, blood vessel. Magnified several diam- 

 eters. (After Kauvier.) 



peripheral lacunar space, the lymphatic sinus, which separates the 

 inner surface of the capsule from the adjacent lymphoid tissue, 

 but which is bridged across at frequent intervals by the fine strands 

 of lymphatic reticulum. 



The lymphoid tissue, which forms the substance of the node, 

 consists of a dense peripheral portion, the cortex, formed by closely 

 packed lymphatic follicles, and a looser medulla in which are co- 

 lumnar accumulations of dense lymphoid tissue, the lymphatic 

 cords. 



Cortex. The follicles of the cortex are partially separated from 

 each other by septum-like trabeculas which extend inward from 

 the fibrous capsule, and along which the peripheral lymphatic 

 sinuses are continued into the substance of the node to partially 

 surround its lymphatic follicles. 



Each lymphatic follicle is thus surrounded, except at its central 

 pole, by a peripheral lymphatic sinus, into which the afferent lym- 



